Worldwide, the most commonly used system for attaching detachable loads to an aircraft makes use of a pair of suspension lugs attached to the load. On the underside of the aircraft is an assembly comprising hooks that fit through the lug eyes. When it is desired to release the load, the assembly on the aircraft is activated to slide the hooks out of the lug eyes allowing the load with the lugs attached to fall away from the aircraft.
FIG. 1 shows a typical load 10 with two suspension lugs 12 attached. In FIG. 2 is shown a standard suspension lug 12. Suspension lug 12 is made from a solid piece of metal and comprises a threaded base 14 to attach it to the load and a lug eye 16 into which the hook fits to secure the load to the aircraft. In most of the air forces in the Western world, the lugs are standard and, depending on the size of the load, conform to the specification Mil-A-8591, which governs all characteristics of the lug, such as physical dimensions, minimum load carrying ability, etc.
In normal use, the lugs are stored separately from the loads. Each load has two standard sized threaded wells located on its top side. The wells are spaced apart by a distance that is standard, and conforms to the specification Mil-A-8591 and are located relative to the center of gravity of the load, such that the load will separate from the aircraft properly when released. When the time comes to attach the load to the aircraft, the load and lugs are removed from storage and brought near to the aircraft. The ground crew screws the lugs into the threaded wells on the load. The lugs are screwed in by hand and are turned until the bottom of the lug eye is level with the surface of the load and the lug eyes are perpendicular to the direction of flight as shown in FIG. 1. The load is then raised under the aircraft and the hooks on the assembly of the aircraft are slipped through the lug eyes.
After releasing the load from the aircraft, the lugs remain attached to the load and make a significant contribution to the total aerodynamic drag on the load as it moves through the air. In modern combat situations it is of critical importance to the completion of the mission and, more importantly, to the safety of the aircraft and its crew to increase the stand-off distance for releasing payloads to the maximum. Therefore a great deal of attention has been given to reducing the drag on the load, thereby allowing it to be released further from the target.
Theoretical calculations, which have been verified by means of measurements combining wind tunnel tests, show that in the typical case of a freefalling payload of the type shown in FIG. 1 the two lugs of the standard type shown in FIG. 2 may contribute up to 16% of the parasitic drag on the load.
The most common technique used in the prior art to reduce the drag caused by the lugs that connect detachable loads to aircraft before release is to modify the load in such a way that the lugs are withdrawn beneath the surface of the load once it is released from the aircraft. Examples of arrangements of this type of varying degree of complexity are disclosed in the following patents U.S. Pat. Nos. 5,056,408, 5,961,075, 3,967,529, and 4,170,923.
Taking into account the vast quantity of loads, especially armament of various types, that are stored at any one time in various locations around the world, the comparable numbers of suspension lugs, and especially the desire and necessity of maintaining standardization so that loads can easily be attached to and released from various types of aircraft, it would be desirable to provide an easy method of reducing the drag caused by the suspension lugs, which would allow the continued use of these available stores and further would allow continued production using existing production lines and standards. Such a method should ideally require no changes to the aircraft or load and should involve minimal changes to the work routine of the ground crews that prepare the loads and attach them to the aircraft.
It is therefore a purpose of the invention to provide a modified suspension lug which will allow loads to be releasably connected to aircraft and will contribute significantly less than standard lugs to the drag on the load after it released.
It is another purpose of the invention to provide a modified suspension lug in which comprises a mechanism that is simple, reliable, and safe.
It is yet another purpose of the invention to provide a modified suspension lug which interfaces to the load and aircraft while complying with the requirements of the widely-accepted standard MIL-A-8591.
It is yet another purpose of the invention to provide a modified suspension lug which can be attached to or removed from the load easily using only standard equipment or tools.
Further purposes and advantages of this invention will appear as the description proceeds.